It is widely accepted by the scientific community that our planet is experiencing a gradual climate change trend with a systematic rise in temperature, which is more pronounced during the last 50 years (Intergovernmental Panel on Climate Change – IPCC, 2018). In addition, in some regions, such as the Arctic or the Mediterranean, the degree of change in the associated processes is higher than the average increase of temperature.
There is an urgent need to intensify the research to investigate all factors that exacerbate or mitigate the effects on the earth-atmosphere energy balance. In particular, there is a limited understanding of the effect of aerosols on the characteristics and properties of clouds (indirect effect) and on their ability to absorb radiation (direct effect), an ability that changes with their ageing. These uncertainties affect both the future climate projections and the estimates of the contribution of various pollutants and other factors to the increase in global temperature and changes of other climatic parameters.
The topic of the PhD thesis is the understanding of the processes that configure, directly and indirectly the aerosols’ optical properties and feedback mechanisms on the local and regional atmospheric system of the Mediterranean. This will be accomplished with a targeted study of the optical properties of aged particles, through time series of observations in characteristic Mediterranean environments along with a comparative study of the background environment, including that of the free troposphere (ACTRIS/GAW Helmos station) and the urban background in Athens (ACTRIS/GAW Athens-Democritus station). Specific phenomena that will be examined among others are the nucleation and modelling to understand the particle condensation to cloud condensation nuclei and their direct effect in radiation transfer (scattering-absorption of radiation), including phenomena such as the wildfires in the Eastern Mediterranean and dust transport from Africa.
The study of the effect of aerosols on the climate for the above cases will be also carried out using advanced radiative transfer models. In parallel, advanced statistical models will be used to identify and extract patterns related to the study of the aerosols’ characteristics and their interaction with the climate over the Mediterranean. The complexity associated with the above interactions requires the use of both linear and non-linear models to derive properties that highlight the role of aerosols in the observed climate change the area of study.